Processing of sludges and the like



May 31, 1932. c. s. BRYAN PROCESSING OF.SLUDGES AND THE LIKE Filed April 15, 1931 Patented May 31, 1 932 UNITED STAT-ES PATENT orFlca' cnaanns s. Bevan, or aunroan, anonn ISLAND, n'ssrenoa 1'0 amour cannon. wonxs, or mmronn, anona ISLAND, A CORPORATION or anonn ISLAND raocnssme or "snunens AND m m ap neaaon an April 15, 1981. I Serial no. 530,219.

This invention involves the processing of slud es,'slurriesor1the like, in which'finely divi ed or crystalline material is suspended in a body of liquid from which it is to be separated as for subsequent processing. In many of these sludges it is highly important tov get, a complete separation of the liquor from the suspended material, in some cases because of the value of the liquor, in others because u left with the solid, and in some instances both considerations are present.-'

While my inventionis useful in the meessing of various materials, I cite as illustrative a by-product calcium sulphate, such for example, as that from acid manufacture,

as this affords not only a very characteristic illustration, but is in itself a product for which my invention is very important and to.

which it is peculiarly-adapted in producing certain very important results. 1

Such a sludge or slurry is also of characteristic importance in that its solid matter is in a very finely divided state due to the fact that it is a precipitate and one found to have unusual properties on account of its very fine crystalline condition.

Certain methods or processes of treatment have been developed which may behest carried on with the material, suchas calcium sulphate, in a water suspension free from deleterious matters and still having its desired crystalline factors of advantage.

In carrying out my invention take" such a sludge or slurry and dewater orifilter it as on a sand bed to which suction is applied" to.

draw through the liquor in which t terial is suspended in the original slurry.

In doing this and for reasons later ap- 4o peering, my invention contemplates a very light non-compacted deposit of material. I therefore allow thematerial to deposit with as little densification of the cake as possible and in so doingthe followingsteps become important. Y

of the deleterious effect of the liquid if partly e. ma-' sistency and while the surface is still plastic In practice as soon as the main body of the supernatant liquid has been drawn throu h the material and the incipient top of the feposit begins to become apparent, I impart to the slurry over the cake a swirling actionby 5o whlch a wave or waves are caused to sweep around the surface, said waves having a rad al resultant tendingto move the material outwardly against the wall of the agitatin chamber from which the material eddies bac toward the center, thus producing a traversmg and re-traversing of the surface of the non-compacted material as it forms.

As this goes on and with the continuing withdrawal of the fluid, there is a continuing thickening of the slurry at the forming surface which becomes. more and more of a plastic until the impellers employed to produce the wave are really pushing or rolling a crest or crests of thick plastic nature over the more solid part of the deposit.

In this way I get a rapid removal of fluid withoutbuilding upa dense or compacted depth of the material. As the material is lightly deposited it offers a minimum of resistance to the passage of the liquid thus requiring a minimum of suction and of power, leaving the material in the fine crystalline state heretofore described as so desirable.

Furthermore, this swirling of the slurry or movement of the plastic wave. prevents the formation of any cracks or, if'cracksv or openingsistart, these 'are promptly closed by the movement of the plastic wave over the sur- .fajcie. a ".When the "charge is of the proper con- I then begin the washing step during which the plasticity of the' surface is maintained and the, deposited material thoroughly washed. As the wave or plasticizing movement is maintained the Washing is eiiectecl without the formation of cracks or loss of material deposited or vacuum. Q

the wash water withdrawn so that the in' cipient surface is again reaching its maximum plasticity, I then add suificient secondary fluid which may be for sus ension for further treatment, continuing t e surface action preferably with increased agitation and progressive stirring or scouring of the material until substantially all of the material is brought into the desired state of suspension.

I then draw or pump off this new suspension which now consists of a material such as the gypsum precipitate in a high degree of purity and in a state of crystalline fineness'. The suspension maynow be processed or're-processed as desired, either as a suspension and later in a concentrated condition according to the ultimate product desired. The material may also be treated or partly treated during the formation of the new suspension.

My invention may be practiced with various'apparatus of various arrangement. As illustrative of a simple form of such apparatus and of the wave formation to be maintained, I have shown somewhat diagrammatically in the accompanying drawings the fol lowing.

Fig. 1 is a sectional view through a settling chamber filled with 'a slurry.

Fig. 2 a similar view showing the slurry substantially deposited with the impeller working on'the plastic top. A

Fig. 3 a similar view showing the wash water added. Y 1

Fig. 4 a view showing the chamber after the wash water is withdrawn and the rotary members working on the plastic top.

Fig. 5 a view showing the chamber with the material re-suspended withthe impellers working, and v Fig. 6 a diagrammatic view showing one of the impellers pushing the wave of the plastic material at the top of the deposit.

In these drawings the apparatus is indicated at 1-the exhaust at 2, the permeable bottom at '3. I have not attempted to indicate difi'erentiations in the condition of the material within the apparatus because as before described this condition is changing throughout successive steps.

From the original sludge or slurry is extracted the original liquid of suspension during which the precipitate is built up lightly asfdescribed intoa deposit with a plastic depth of upper surface. This in turn is washed and-then re-suspended and removed.

The wave action is produced by impellers such as 4. I may also provide agitators 5 and pulping members 6. all of which may be raised and lowered as indicatedby the arrows to bring them to-the proper level or J5 depth as the action goes on.

The wave impellers 4 when in action are working on the plastic up er depth ofthe .deposit or incipient top 0 the deposit, but

may be used asstirrers either alone or with the agitators 5' and the pulpers or scrapers 6 WhlCh are lowered as material is a in brought to suspension as above describe The apparatus may be of varied form and the steps arranged or varied. From any such va riants if in accordance with the invention, the resultant product will be of the desired characteristics.

In the step of washing there is, of course, a tendency in the plastic depth to re-suspend but even if there is a slight re-sus nsion in the wash water it is at once carrie into and left with the previously deposited material so that there is in practice no appreciable loss. What I therefore claim and desire to secure by Letters Patent is 1. In the rocessin of sludges, slurries or the like, of nelv divi ed or crystalline material such as precipitates, those steps consisting in withdrawin the liquor to efiect a light, non-compacte deposit of the material having a plastic surface, in maintaining a plasticizing movement of the surface of the deposit while maintaining that portion of the deposit'remote from the surface undisturbed, and in washing the deposit while continuing the surface movement thereof and while maintaining the surface of the deposit plastic.

2. In the rocessin of sludges, slurries or the like. of fiirely divi ed or crystalline material such as precipitates, those steps consisting in progressively withdrawn the liquor of the original recipitate to effect a light, non-compacted deposit of the material having a plastic surface, in maintaining plasticizing movement of the surface circumferentially of the deposit while maintaining that portionof the deposit remote from the surface undisturbed during withdrawal of the liquor, in washing the deposit while continuing the surface movement thereof and withdrawing substantially all of the wash water while continuing the surface movement of the deposit.

3. In the processing of sludges, slurries or the like. those steps consisting in withdrawing the liquor from the original sludge leaving a deposit having a plastic surface, in maintaining a plasticizing movement of the surface of the deposit during withdrawal of the liquor and while maintaining that portion of the deposit remote from the surface undisturbed. i

4.. In the processing of sludges, slurries or the like, those steps consisting in withdrawing the liquor from the ori 'nal slud leaving a deposit having a p astic sur ace, in maintaining a (plasticizing movement of the surface of the eposit during withdrawal of the liquor and while maintaining that portion of the deposit remote from the surface undisturbed, and in then washing the deposit. 5. In the processing of sludges, slurrles or the like, those steps consisting in withdrawing the liquor of the original precipitate to effect a deposit of the material in a nondensified condition having a plasticsurface, in maintaining movement of the surface of the de- 10 posit during Withdrawal of the liquor and while maintaining the bottom portion of the deposit undisturbed, and in washing and draining the deposit while continuing the surface movement thereof. 15 In testimony whereof I aflix my signature.

CHARLES S. BRYAN. 

